Google Adsense

Our website that this weblog belongs to has shown a significant improvement in search engine results since I implemented an optimisation programme at the beginning of August. Visitor numbers have trebled and are consistently in three figures per day. I did have adsense on this blog and parts of the website but have now restricted them to two unpromoted websites I own. This I did after reading an article where it was suggested that Yahoo and some of the other search engines were possibly penalising websites that displayed google adsense advertisements. I was not making a fortune out of these but it did amount to about $5 per day which is always welcome additional income. Does anybody else think this may be happening? Or is this simply scaremongering? So many rumours about search engine practices seem to fly around it is difficult to know what to believe. Another one is the alteration of the google spider so that it will only pick up relevant content links back to websites. It would seem from my own experience of my own website that this is true for google until I look at the link backs for some of my major competitors which in some cases run into many thousands. When these links are checked they are mainly for properties in Bulgaria and Spain. To my mind these are not relevant links to a cleaning company based solely in the UK? Am I completely wrong in my thinking? Has anyone anything further to add to this? Either to clarify or muddy the waters even more! Your comments are most welcome.